Induction heater



Jan. 8, 1935. J, L. ADAMS, JR

INDUCTION HEATER Filed NOV. l6, 1928 4 Sheets-Sheet 1.

R o v T N E V m Jan. 8, 1935.

J. L. ADAMS; JR

INDUCTION HEATER I Filed Nov, 16, 1928 4 Sheets-Sheet 2 INVENTOR Jan. 8, 1935; J, L, A A 4R 1,987,458 INDUCTION HEATER Filed Nov. 16, 1928 4 Sheets-Sheet 4 7 III/III/IIIII/III/II/IIIII/l/ III/Ill III/IIIIIIIIIIlI/I/I/I/II/I/IIM/III/b Y Y A5 Patented Jan. s, 1935 I e 1,987,458

UNITED STATES PATENT OFFICE INDUCTION rms'rsa James L. Adams, In, Youngstown, Ohio, assignor to .The Youngstown Sheet & Tube Company, Youngstown, Ohio, a corporation of Ohio Application November16, 1928, Serial No. 319,800

11 Claims. (Cl. 219-13) My invention relates to electric induction out any given portion of the article, as will be heaters, and more particularly to an induction hereinafter more fully set forth. heater for metallic shapes of substantially tubular My invention also lends itself to an accurate or substantially continuous peripheral contour, control and timing of the energy input to sucalthough the utilityof the invention-is not limited cessive articles, whereby uniform. temperature 5 in this respect. conditions in corresponding parts of successive In heating the ends of tubular metallic shapes articles are insured. This permits such articles such as pipes, columns and other hollow bodies, to be shaped under uniform temperature condipreparatory to. shaping the ends thereof for formtions and insures retention of this uniformity l0 ing bells, collars, flanges, and the like, it has after cooling. By the use of the combustion l0 heretofore been customary to use gas or oil method of heating, there has been such a nonflames. The use of such flames for this purpose uniformity of heating that although successive has been accompanied by considerable losses in shapes were subjected to similar shaping operatime and thermal energy. The use of a gas flame tions at the temperatures to which they were requires a continuously moving column of gases supplied to the shaping apparatus, they assume it; heated to the same temperature as the end of different conditions upon cooling due to difference the shape in order to remove the products of in the initial temperatures therein. combustion from around the ends of the shape, The present invention also possesses inherent and the heat carried away by such a moving advantages over the heating by combustion in column of gases is wasted. Such a flame also that oxidation and scale formations are func- 20 heats the metal comparatively slowly so that the tions not only of the duration of the heating peradiation and conduction from the heated porriod but of the characteristics of the heating 01 the Shape kes place for a relatively lo g atmosphere. By the use of an induction heater,

. time. It is also difiicuit to concentrate the heat the period of heating is reduced and the article from such a flame over a definite area, and it is is subjected to atmospheric conditions less con- 25' likewise diflicult to obtain uniform heating ducive to the formation of scale. throughout any substantial area of a given ob- It will also be apparent to those skilled in the ject, or uniformity in successive object's. art that an inductionheater lends itself to en- I provide an electric induction heater for metal closure within a suitable room or casing in such 0 shapes, the heater being of such construction that manner that the access of air currents 0 th a portion of the shape'to be heated is adapted to article during the heating period may be rebe included within a magnetic circuit in such duced to a, minimum or entirely elimina edmanner that the metal the Shape co tutes In order to insure the desired concentration of either a closed or an open secondary circuit, (18- energy in predetermined portions of an article 5 pending upon the characteristics of the shape. undergoing treatment, I provide a magnetic cir- The area of the shape which is heated is subject cuit preferably including only a single air gap and to exact control by the extent to which it is insubstantially embracing a primary coil to which eluded within the magnetic circuit of the heater. operative access is had through the gap. I also By concentrating magnetic lines of force in preferably construct the gap so that it substansuch area, the metal composing the same is tially conforms bothtothe inside and outside con- 40 rapidly heated without the heat losses incident tour of the article being heated, and so form the to combustion heating. In actual practice it coil as to impart similar characteristics thereto. has been found that from one-eighth (i 8th) to The invention contemplates, however, the possione-twelith th) as much time is required for bility of so shaping the coil as to affect the conthe heating of an article in accordance with the trol of the thermal energy input in different por- 45 present invention as that required for the heattions of a single article. By reason of the tremening of the same article to a corresponding temdous energy concentration herein contemplated, perature by combustion. By reason of this dif- I provide cooling means preferably interlocked ierence in time alone, it will be apparent that with the electrical circuit in such manner that heat losses due both to radiation and conduction cooling is automatically accomplished eoncorni- 50 are materially reduced. At the same time, the tantly with each heating operation.

distribution of heat throughout the entire area In the accompanying drawings I have shown is subject to accurate control so that uniform for purposes of illustration only, and not by way temperature conditions, or difl'erential temperaof limitation, certain preferred embodiments of ture conditions at will, may be obtained throughthe present invention, it being understood that 66 changes in the construction and operation therein illustrated may be made without departing either from the spirit of the invention or the scope of my broader claims.

In the drawings:-

Figure Us a longitudinal sectional view, partly in elevation, of an induction heater constructed in accordance with the present invention;

Figure 2 is a front elevation of the heater of Figure 1;

Figure 3 is a rear elevation of the heater of Figure 1;

Figures 4 and 5 are detail sectional views of a portion of a primary coil of modified characteristics shown in operative relation to an article being heated, and

Figure 6 is a view similar toFigure 1 ofa modifled embodimentof the invention.

In carrying'out the present invention there may be provided an induction heater comprising a frame or yoke 2, herein illustrated as being of substantially E-shape, although -other constructional shapes may be utilized if desired. The outer legs 4 and 5 of the frame cooperate with a central leg 6 which leg serves as a core about which a coil 7 of wound copper straps or bars is mounted. The legs 4 and 5 are provided with transversely extending pole pieces 8 suitably secured to the legs, and shaped to provide an opening 9 in axial alignment with the leg 6. The size and configuration of the pole pieces 8 as well as the size and configuration of the core 6 is initially determined by the size and contour of the article to be heated, the parts preferably being so related as to provide a polar air gap of as moderately short radial lengths as is consistent with the expeditious insertion thereinto' and the removal therefrom of the article to be heated, although the dimensions of this gap may be materially changed without departing from the advantages inherent in the present invention.

The core 6 is preferably formed by the building-up of individual lamina or plates 11 of dif ferent widths and securing them together in any "desired manner, as by bolts 12, suitably insulated therefrom, so that the finished structure provides approximately the contour required.

The air gap 9 thus formed is adapted to receive the end portion 13 of the article to be heated as indicated in Figure 1, such article preferably being inserted a distance such that substantially all of the convolutions of the'primary coil 7 are effective thereon. Inasmuch as the efliciency of a coil of the character herein illustrated increases appreciably as it more closely approaches the outer periphery of the article being heated, I preferably so construct the coil as to lie as closely adjacent such article as is possible, preferably making allowance only for the variations in dimensions permitted by commercial tolerances.-

Assuming for example, that a heater in accordance with the present invention isbeing utilized for the heating of soft steel pipe ends having an outside diameter of 12 inches and an inside diameter of 12 inches, and that the heating is to be effective over a zone approximately 6 inches wide in a direction axially of the pipe, and that such area is to be raised to a temperature of approximately900 to 1000 degrees 0., I may utilize either a periodically varying direct current circuit or an alternating current circuit such as an volt 80 cycle circuit, utilizing 700 k. w. initial capacity and k. w. final capacity. giving a mean value of about'350 k. w.

be effected in a period of from 30 to 40 seconds.

It will be apparent to those skilled in the art fore becomes apparent that the question of the dimensions of the air gap' between the interior of the primary coil 7 and the outside of the portion 13 of the article being heated is of extreme importance. If too great a cross magnetic leakage takes place through such air gap, the k. w. input into the heater becomes too low unless the input voltage is correspondingly increased. In order to effect as great a k. w. input as possible, and also by reason of the great radiation temperatures met with in the primary coil, the inner surfaces of the copper straps 7 are left bare. By reason of this construction it is possible to obtain the desired proximity between the primary coil and the secondary surface.

It will be noted that in Figure 1 of the drawings,

the primary coil is illustrated as having each of the turns- 7, although it may be positioned internally of such turns, or the'turns may be of divided construction with the cooling duct intermediate the irmer and outer surfaces.

A tube 15 of insulating material, such as micarta, may be disposed around the outer surfaces of .the ductl4 and within the legs 4 and 5 of the frame 2. This tube is effective for supporting the duct'14. and may be in turn held in position by suitable straps or bracketsl5', as illustrated in Figure 3. I

One end of the duct is shown as connected by a flexible hose 16 of non-conducting material, such as rubber, to a supply valve 17, having a control means 18 projecting therefrom. The other end of the duct 14 is connected to a ground 19 and to a discharge pipe 20, although it will be understood that the ground may be at a suitable mid point of the coil, and that the duct may be so constructed as to provide a plurality of portions having a parallel flow therethrough.

The coil is supplied with electrical energy by conductors 21 and 22 connected through a switch, contactor or suitable circuit breaker 24 to a supply circuit 25. As before indicated, this supply circuit may comprise a suitable source either of alternating current or of proper periodically varying current, as may be desired. The conductor 22 also has a connection 26 to the ground 19.

The circuit interrupter 24, or its operative equivalent, may be provided with an operating connection 2'! extending between the same and the operating means 18. It may also be provided with a core 28 positioned to be operated upon by a solenoid29 having the current thereto controlled by a rotating contactor drum 30. This drum is herein illustrated as driven by a worm wheel 31 from a worm 32 on the shaft 33, of a suitable motor 34.

The contactor drum 30 may be of such construction as to-periodically close and open the solenoid circuit in any desired time periods. By reason of thisconstruction, it will be apparent that when the solenoid circuit is energized, the core 28 will be moved upwardly against the action of the spring 35 and thereby eflect a closing of the circuit to the primary coil and an opening of the valve 17 by means of which the supply of cooling fluid is delivered to duct 14. This condition will continue for a predetermined time interval dependent upon the construction of the contactor drum, which will be effective after the desired length of time for opening the circuit to the solenoid and thereby breaking the circuit to the primary coil 7 and closing the valve 1'7, although it will be understood that the water or other cooling fluid may be continuously passed through the duct if desired. It will be understood that a suitable signal may be provided if desired for the purpose of indicating to the operator of the apparatus each time the circuit is broken and the heating completed, so that the heated article may be removed and a fresh article inserted preparatory to the following heating period.

The conducting segment on the drum 30 is tapered as shown in Figure 1. By swinging the relatively fixed contact finger engaging the segment, the duration of, and the time intervening between, successive periods of energization of the inducing coil may easily be varied.

In Figure 4 I have illustrated a portion of a coil 7' in operative relation to a portion of the article 13' to be heated. In this figure the coil is shown as having the central portion thereof so constructed as to provide a slightly greater distance between the coils thereof and the periphery of the article.

In Figure 5 there is illustrated a coil 7' in cooperative relation to a portion of an article 13", the coil in this embodiment of the invention being constructed in such manner that the end portions provide a slightly greater gap with respect to the article. than does the central por tion.

These figures are representative only of different forms which the primary coil may assume for controlling the exact heat distribution throughout any portion of the article being heated.

In Figure 6 I have shown a modification oi the invention particularly adapted for use with large diameter pipe having greater wail thicknesses. An inner coil 36 is mounted on the core 37. An outer coil 38 is mounted within the legs t and 5 in substantially the same manner as the coil 7 shown in Figure 1. The inner coil is provided with cooling ducts 39, and cooling ducts 40 are formed on the coil 38. The outer surface of the coil 36 and the inner surface of the coil 38 to concentrate a greater amount of thermal energy in the pipe in a given space than is possible by the use of either coil alone. The operation of this, form of the invention is substantially the same as that shown in Figure 1; and the circuit connections showntin Figure 1 are also applicable to this form of the invention.

While in the form .ofmy invention illustrated in Figure 6 I have shown the cooling ducts 39 and 40 positioned inside and outside of the respective coils with which they cooperate in order to permit the coils to assume a position as close to the article being heated as possible, it will be apparent that operatin'g conditions may dictate the necessity of utilizing cooling ducts otherwise disposed.

depending upon the exact construction of the coils utilized. In this respect, therefore, the figure of the drawings is illustrative only of one form of construction which may be utilized in carrying out my invention.

Certain advantages of the present invention arise from the provision of an induction heater by means of which the energy input may be concentrated throughout a given area so as to produce either uniform heating throughout that area or differential heating of diflerent portions of the area.

Other advantages of the invention arise from the provision of an induction heater of the character referred to in which cooling means is provided in such manner as to permit the concentrated heating action desired without danger of injury to the apparatus.

Further advantages of the invention arise from the provision of an induction heater in which 20 the cross-magnetic leakage is reduced to a minimum, thereby insuring a high operating eiiiciency and in which access to the heating :zone is obtained through a single air gap of' constant cross-sectional characteristics.

.Still other advantages of the invention arise from the provision of a heating apparatus in which the cooling of the coil or coils may be correlated to the flow of current therethrough in such manner as to prevent the passage of current through the coil or coils without bringing the cooling means into operation.

Still other advantages of the invention arise from the provision of an induction heater in which there is a magnetic circuit including a single air gap with a coil, or plurality of coils. within said circuit and substantially embraced thereby in such manner that operative access to the coil or coils is had by inserting the article to be heated through such gap.

1' claim:--

1. ii an electric induction pi axially elongated. liquid -c is wound circumierentisdly uvithe surface contour of said the axial length of said coil so small air-occupied gap only tin. csetween, a stantially closed laminated magnetic circuit surrounding said coil on both in. and outside thereof except for a single nae cw annular air -end heater, an inducing coil gap in axial alignment with above mentioned air gap and giving free access to the inducing zone at all times by the pipe-end to be heated, means for supply of periodically variable current to said inducing coil, and means for accurately aligning said inducing coil axially with said annular air a 8 2 In an electric induction pipe-end heater, 0. liquid-cooled inducing means comprising two circumferentially wound but slightly radially spaced coil sections located respectively on inside and outside of said pipe-end and close to the respective surface contours of latter throughout the axial length of said coil sections. said sections being in substantially the same transverse plane with respect to pipe axis, a substantially closed laminated magnetic circuit encircling said coil sections except for a single narrow annular and axially directedair gap aligned axially with the narrow annular air-'-space between said coll sections, and means for supplying periodically variable current to said coil sections, said narrow magnetic air gap being freely accessible at all times to said pipe-end without'structural changes;

axially elongated and radially shallow watercooled inducing coil wound circumierentially with and very close throughout tovthe surface contour oi the pipe-end to be heated so as to give very low magnetic leakage, a very narrow annular air gap in an otherwise substantially closed laminated magnetic circuit surrounding said coil on both inside and outside thereof, said air gap supplying free-access at all times to said pipe-end without shifting of parts, means for supplying periodically variable current to said coil, means for determinately graduating the point-to-point temperatures attained along said pipe-end, and means for timing successive heating periods.

a. In an electric induction pipe-end heater, two axially elongated and radially shallow watercooled inducing coils wound concentric with each other and peripherally with the pipe-end to be heated but radially spaced veryslightly' in the same plane transverse to pipe axis so as to provide free access of said pipe-end therebetween, a laminated magnetic circuit substantially en closing said coils except for a single narrow annular pipe-guiding air gap therein axially aligned with the annular space between coils and providing free access at all times to said pipe-end, means for supplying periodically variable current to said coils, means for determinately grading the heating back from the pipe-end as desired, and means for determining equal energy supply to successive heats.

5. In an electric induction pipe-end heater, a liquid-cooled inducing means comprising two circumierentially wound but slightly radially spaced coil sections adapted to receive a pipe-end therebetween and close to the respective surface contours thereof throughout the axial length of said coil sections, means for effecting the shading oil of the heating back from the extreme pipe end, and means for supplying periodically variable current to said coil sections.

6. In an electric induction pipe-end heater, a pair of inducing coils relatively elongated axially andlying substantially in one common radial plane but spaced apart very slightly to just permit the free entrance at all times of a pipeend to be heated, a laminated magnetic circuit substantially enclosing said coils except for one narrow circular air-gap through which said pipe end at all times has free access to its position between said coils, a laminated core inside the inner coil, said core being supported in align-,

ment with said air-gap and completing the interior portion of said magnetic circuit, and a source of periodically varying current connected menace to both ofsaid coils so as to cumulatively excite said magnetic circuit.

7. In an induction heater, an inducing coil wound so as to lie peripherally very close to a tubular work-piece to be heated, a laminated magnetic circuit substantially enclosing said coil all around except for a shallow circular air-gap providing free access of said work-piece at all times to an operative inductive position closely adjacent to said coil surface, and means for sup-. plying periodically variable current to said'coil, the latter being characterized by a predetermined variation in the clearance distances of the several turns to the work-piece, for local regulation oi the temperatures attained therealong.

8. In an electric induction heater, a primary inducing coil adapted to receive a work-piece to be heated, a substantially closed magnetic circuit embracing said coil, said circuit having an airgap permitting introduction oi the work-piece, means for connecting said coil to a source of periodically varying current, means for operating said connecting means at predetermined time intervals, and means for adjusting the time interval between successive operations of said operating means.

9. In an electric induction heater, a primary inducing coil, means for supplying periodically varying current thereto, said 0011 being adapted to receive a work-piece, and an adjustable timing mechanism for periodically rendering said cur-- rent supply means efiective.

10. In an electric induction pipe-end heater, a relatively elongated primary inducing coil, means for connecting a source of periodically varying current to said coil, a substantially closed magnetic circuit embracing said coil and having an air-gap adapted to receive a work-piece to be heated, means for periodically operating said connecting means, said operating means-including means for varying the length of time during which the connecting means are operated.

11. In an electric induction pipe-end heate two relatively elongated, co-axial primary induc ing coils, said coils being adapted to receive an annular work-piece therebetween, a magnetic circuit embracing the coils, and an annular air-gap in the circuit adapted to receive the work-piece, said coils being so connected to a common source of periodically varying current as substantially to minimize magnetic leakage between the cells when the work-piece is not disposed therebetween, by opposing their magnetizing iorces in the inter= vening space.

- JS L. AD, JR. 

